Method of making propeller blades



1934- J. SQUIRES 1,942,223

METHOD OF MAKING PROPELLER BLADES Filed March 11, 1931 INVENTOR /M%NEY$- MP4 Patented Jan. 2, 1934 UNITED STATES PATENT OFFlCE 7 Claims.

This invention relates to propeller blades such as are employed in connection with propellers of aircrafts and the like and particularly to an improved method of manufacturing propeller blades.

The main objects of the invention are to provide a method for forming a propeller blade from a rectangular sheet-like piece of metal stock of substantially uniform thickness, to provide a method of this kind in which the sheet-like piece of stock is initially formed into a hollow cylindrical blank having a welded seam; and to provide a. suitable operation for working the ridges of metal that are formed on the inner and outer sides of the tube, during welding of its seam, to the contour of the inner and outer peripheries of the tube respectively in a manner which improves the texture or grain structure of the metal.

Other objects of the invention are to provide an improved propeller blade forming method in which the welded cylindrical blank is modified into a tubular blank of non-uniform diameter and one end thereof is deformed so as to provide a flange for securement to a propeller hub; to provide a suitable machining operation for modifying the wall thickness of the blank of nonuniform diameter to substantially that desired in the finished product; to provide a machining operation of this kind in which the walls of one end of the blank are reduced to a lesser thickness than the remaining portions of the blank and in which the welded seam of the blank is trimmed throughout its entire length to conform with the exterior of the blank; and to provide a subsequent operation for closing and welding closed the end of the blank having the thinnest wall.

Further objects of the invention are to provide a final die forming step in this improved method, in which the blank is pressed to the desired cross sectional contour with.the welded seam thereof located in a position with respect ,to the-dies that causes the seam to lie in a predetermined location in the ultimate blade; and to provide for the placement of the welded seam of the blank in that portion of the blade at which minimum strain occurs.

An illustrative embodiment of the invention is shown in the accompanying drawing, in which:

Fig. 1 is a plan view of a piece of stock from which a tubular propeller blade blank is formed.

Fig. 2 is a side elevation of the stock showing the uniform thickness thereof.

Fig. 3 is a perspective view of the piece of stock ihgwn in Figs. 1 and 2 formed into a cylindrical 'the blank to form a securing flange.

Fig. 7 is a view similar to Fig. 5 showing the blank as modified in Fig. 6 supported on a mandrel and being machined to bring the wall thick ness thereof to the desired dimensions.

Fig. 8 is a central vertical section of a propeller blade blank which has been machined to desired dimensions.

Fig. 9 is a fragmentary vertical section similar to Fig. 8, but illustrating the method of closing the small end of the tube.

Fig. 10 is a transverse vertical section of a tu-- bular blank showing the same positioned between a pair of dies in readiness for compression to final blade shape.

Fig. 11 is a view similar to Fig. 10, but showing the die parts brought together and illustrating the manner in which the cross-sectional shape of the blank is modified by the dies.

Fig. 12 is a perspective view of a conipleted propeller blade illustrating the position in which the welded seam of the blade lies.

In the form shown, a rectangular piece of sheetlike metal stock 1 of uniform thickness as indicated in Figs. 1 and 2 is formed into a hollow cylindrical shape, as indicated in Fig. 3, with the side edges thereof brought into abutting, or substantially abutting relationship. Any suitable method of carrying out this step may be employed.

A mandrel 9 is inserted into the tube and the abutting edges of the stock are welded together while the tube is supported on the mandrel by an electric welding process or in any other suitable Way. When the welding process, illustrated in Fig. 4 is employed, electrodes 10 and 11 of an electric circuit (not shown) are applied to the respec-. tively opposite side of the seam while the blank is passed between rollers 9. The electrical resistance of the metal brings the abutting edges of the seam to a welding temperature and the rolls 9 force the,edges together. The edges of the stock are fused together and the fused metal fills in any gap which may have existed therebetween forming a welded seam 10'. Other apparatus may, of course, be' employed for carrying out this same. type of welding operation, it being understood that I prefer the type of welding shown merely because I have found that a more perfect product generally results, but it is to be understood that, other welding methods and apparatus may be employed where desired.

The tube 12 is then modified so as to bring its inner perimetrical dimensions, in planes transverse to its length, into substantial conformity with the inner perimetrical dimensions of the desired finished propeller blade at corresponding sections over its length. Accordingly the shape, size and contour of the inner surface of the blank will be predetermined by the propeller blade shape desired. In the present case, by way of iilustration only, it will be assumed that the desired finished blade shape requires a blank such as is indicated in Fig. 5, and which blank includes a main portion of generally cylindrical conformation and a tapered end portion 13. The particular method of forming the blank from the cylindrical tube and the preferable steps subsequent to the formation of the blank in order to bring it to the desired'blade shape forms the subject matter of other applications for Letters Patent of the United States filed by me, preferably the method disclosed in that one thereof entitled Method of making propeller blades, filed May 20, 1930, Serial Number 454,138. The method therein disclosed will therefore be described hereinafter as constituting the steps preferably employed herein.

Accordingly, the cylindrical tube 12, formed as explained in connection with Figs. 1 to 5 inclusive, is first swaged, rolled, or pressed between suitable dies or otherwise brought to the modified conformation indicated in Fig. 5. In changing the tube of the shape shown in Fig. 5 a mandrel of predetermined size and contour may, if desired, be employed within the tube so as to approximately predetermine the interior size, shape and contour of the blank. During the modifying operation the small end of the tube is not completely closed but it is brought to a relatively small diameter which may be 1.25 inches in a blade which is in the neighborhood of five feet long. Furthermore, as will be apparent, the modifying operation also increases the wall thickness of the reduced end of the tube as the diameter is decreased, as indicated in Fig. 5.

The ridges of metal which are generally formed on the outer and sometimes the inner side of the blank 12 duringthe welding operation, are preferably worked by hammering or swaging operations to the contours of the outer and inner peripheries, respectively, of the tube 12. Working of the metal at the scam, in this manner, produces a grain structure which is desirable in articles of this kind.

The tube or blank 12 is then placed ina suitable die such as indicated at 14 in Fig. 7 and operated upon by a plunger 15 or other suitable apparatus so as to deform the large end of the blank to provide thereon the radially extending annular flange 16. Sufl'lcient metal is preferably upset to impart to the flange 16 a thickness greater than the original thickness of the wall of the blank 12.

During reducing of the small end of the blank and consequent thickening of the metal thereof, it often happens that gathers, ridges or serrations are'internally formed in the nose portion, and consequently, it is desirable in such cases at least that the nose portion of the blank be internally 'I find that it is generally preferable, that ,the'

end portion only of the tube be tapered as above 30 described leaving the greater portion of the. length of the tube of uniform diameter, this being mainly desirable from a standpoint of economy in production. On the other hand, I find that, from the same standpoint, during the following operations, it is desirable that the blank be ta.- pered, although not necessarily uniformly, from the small end thereof to the opposite end. This may best be accomplished by bringing the blank to a suitable temperature and then forcing into it a mandrel such as indicated at 17 in Fig. '7. This mandrel preferably has a nose portion conforming exactly in size, shape and. contour to the size, shape and contour of the pre-machined nose portion above referred to, the remainder of the mandrel being of a tapered conformation conforming to the desired size, sha and contour of the remainder of the interior 0 the blank ultimately to be formed. When this mandrel is forced into the heated blank, it not only expands the previously cylindrical portion of the blank but also exerts a certain amount of longitudinal stretching action on the blank, I find that this is desirable because of the fact that in stretching the main portion of the blank, the mandrel causes the blank to more closely conform thereto. Although in some cases the nose portion of the blank may be stretched in this manner by making the nose portion of the mandrel slightly larger than the pre-machiued internal size thereof, I find that, because of the reduced dimensions of the nose portion, such stretching action is relatively difficult to obtain in this portion of the blank and consequently this is the reason that I prefer to make the small 115 or tapered end portion of the mandrel conform exactly to the size, shape and contour of the pre-machined internal surface at the small end of the blank.

The mandrel 1'7, or another mandrel which 120 conforms exactly to the inner size, shape and contour of the blank 12, with the blank 12 thereon is then positioned between suitable centers 18 and 19 in a lathe or other machine and the blank 12 is externally machined by a tool 20 which 125 is suitably guided in a predetermined path with respect to the external surface of the mandrel 17 so as to bring the wall thickness of the blank to the desired dimensions.

It will be observed that under ordinary conditions the wall thickness of the unfinished blank 12; shown in Fig. 5, is preferably slightly larger or thicker than the desired maximum thickness of the walls of the substantially finished blank, shown in Fig. 8, and that during the tapering operation to bring the blank to the condition shown in Fig. 5, the small end of the blank will ordinarily be thickened, whereas in the finished product the maximum thickness is desired at the large end and it is desired to have the wall thickness decrease from the large end of the blank to the small end thereof.

This modification of the wall thickness is accomplished as indicated in Fig. 7, by supporting the blank over its entire length on the mandrel 17 which is in turn supported at both ends between centers. By employing this method it is possible to accurately predetermine the wall thickness of the blank from one end to the other end thereof. I

polish by any suitable operation conveniently employed for such purposes. The blank is next put on a mandrel 21, shown in Fig. 9, which like the mandrel 17, conforms to the internal size.

shape and contour of the blank 12 but which has.

a rounded small end 22 that is located slightly inwardly from the small end of the blank. The mandrel 21 is mounted in a lathe or other suit able apparatus with the small end of the mandrel and blank supported on a steady-rest 23 and the blank and mandrel are rotated.

A flame 24 from an acetylene or other heating torch is then directed at the small projecting end of the blank 12 until the same is brought to a plastic or semi-plastic condition, and then the projecting end of the blank is spun around the end 22 of the mandrel 21 by a spinning tool 26. By this operation the small open end of the blank 16 is closed and the metal is worked to a single point on the axis of the blank and any possible aperture that might otherwise occur at this point is closed by the metal welding into itself. Other means and methods may be employed for closing the small end of the blank, when found desirable or necessary.

After the small end of the blank is closed, then the blank may be placed between suitable die parts 2'7 and 28, in the manner illustrated in Fig. 10, with the welded longitudinal seam 10' so located as to throw it into a predetermined location in the finished blade relative to the leading or trailing edges thereof. As a means of illustration 1 have shown the seam 10' as located in a vertical plane which passes through the central axis of the blank, and on that side thereof which will bring the seam substantially into the center of the pressure face of the propeller, this being one location that I have found desirable in that ordinarily it will be subjected to a minimum amount of strain inthis location. The die parts 2'7 and 28 are provided with cooperat ng depressions 29 and 30, the combined perimeter of which at any particular cross-section of the dies corresponds exactly to the perimeter of the blank 12 at that point. The die parts 2'7 and 28 are then brought together, preferably while maintaining the interior of the blank 12 under suitable pressure and in a heated condition. The die parts 27 and 28 form the blank to the blade shape shown in Figs. 11 and 12. The welded seam may be placed at any other selected location in the blade by suitably positioning it with respect to the die parts 2'7 and 28 before the latter are brought together.

Formal changes may be made in the specific embod ment of the invention described without departing from the spirit and substance of the broad invention, the scope of whichis commensurate with the appended claims.

What I claim is:

l. The method of making a propeller blade from a sheet-like piece of metal stock which consists in formng said stock into a hollow blank, welding the seam of said blank, contracting said blank circumferentially to tapered formation by upsetting the metal of the wall thereof to a greater thickness, modifying the wall thickness of said blank to substantially that desired "n the finished product, closing one end of saidblank, and modifying the cross-sectional shape of said blank between dies, with said welded seam located in a predetermined position, so as to bring the blank to the desired finished cross-sectional contour.

2. The method of making a propeller blade from a sheet-like piece of metal stock which consists in forming said stock into a hollow blank, welding the seam of said blank, supporting successive adjacent portions of said blank internal- 1y against decrease beyond progressively decreasing diameters respectively, working the blank into a tube of non-uniform diameter, modifying the wall thickness of said blank to substantially that desired in the finished product, closing one end of said blank, and modifying the cross-sectional shape of said blank between dies with said welded seam located between the lateral edges of the concavities ofsaid dies so' as to bring the blank to the desired finished cross sectional contour and to position the welded seam of the blank between leading and traling edges of the resulting blade.

3. The method of making a propeller blade from a sheet-like piece of metal stock which consists in die forming the intermediate portions of the stock into a substantially semicircular cross sectional contour, arcuately bending the side portions of the stock inwardly to place the edges thereof in juxtaposition and to form a hollow cylindrical blank, welding the adjacent edge portion of said stock, modifying the perimetrical dimensions of said blank, modifying the wall thickness of said blank to substantially that desired in the finished product by removing stock from the exterior of said blank, closing one end of said blank, and modifying the cross-sectional shape of said blank between dies with the welded edges of said stock' located between the lateral edges of the concavities of said dies so as to bring the blank to the desired contour and to position the welded edges of the stock between the leading and trailing edges of said blade.

4. The method of making a propeller blade from a sheet-like piece of metal stock which consists in die forming the intermediate portions of the stock into a substantially semi-circular cross sectional contour, arcuately bending the side portions of the stock inwardly to place the edges thereof in juxtaposition and to form a hollow cylindrical blank, welding the adjacent edge portions of said stock, working at least one end of said blank to a generally tapered formation, machining the exterior of said blank to bringthe wall thickness thereof to substantially that desired in the finished product, closing the tapered end of said blank, forming a radial flange on the other end of said blank for securement to a propeller hub,-

and pressing the blank between dies with the welded edges of said stock located between the lateral edges of the concavities of said dies so as to bring the blank to the desired cross sectional contour and to locate the Welded edges of the stock at a position of low strain in the blade.

5. The method of making a propeller blade from a planular sheet-like piece of metal stock of substantially uniform thickness which consists in forming the stock into a hollow cylindrical blank, welding the edges of said stock, modifying the blank to one of non-uniform diameter and predetermined internal dimensions, placing said blank upon a mandrel conforming 'exteriorly to the interior of said blank, machining the exterior of said blank by means of a tool maintained in predetermined relation with respect to the surface" of said mandrel, heating one end of said blank to a substantially plastic condition and simultaneously working it closed, and pressing said blank between dies with the welded edges f said stock located in a predetermined position with respect to said dies so as to bring said blank to the desired finished contour.

6. The method of making a propeller blade from a planular piece of sheet metal stock which consists in modifying said stock into a hollow blank of tubular formation with opposite side edges of said stock in abutting relationship. welding the abutting edges of said stock together, supporting the wall structure of said tubular blank internally against collapsing beyond a predetermined tapered contour, modifying the contour of said blank substantially to conformity with said tapered contour, closing one end of said blank, and changing the cross-sectional eontour of the resulting tapered blank to that desired in the finished product and with the line of weld located approximately midway between the leading and trailing edges of said finished product.

7. The method of making a propeller blade from a planular piece of sheet metal stock which consists in modifying said stock into a hollow cylindrical tube with the opposite side edges of said stock in abutting relationship, welding the abutting edges of said stock together, supporting the inner periphery of the wall structure of said 'tube against collapsing beyond a predetermined tapered contour, modifying the contour of said tube substantially to conformity with said tapered contour, removing metal from the exterior of the resulting tapered tube to a depth substantially uniformly spaced from the inner periphery thereof so as to produce the wall thickness desired in the finished product, and forming the resulting modified tube to the desired blade shape with the line of weld located approximately centrally of the pressure face of the blade.

JOHN SQUIRES. 

